Chain tightener



`A. R. AsKUE CHAIN TIGHTENER Filed April '7, i941 April14, 1942.

INVENTOR. /i/.Ezz 7 .ALs/ 05 A Trag/vs rs Patentecl Apr.` 14,l 1942 iCHAINTIGHTENER AlbertV R. Askue,`Mentor, Dhio, assignor to TheACleveland Trencher Company, Cleveland, Ohio,

a corporation of Ohio Application April 7, 194i, Serial No. 387,165

7 claims. l(ci. 'r4-242.11) r `This invention relates to `atrenchdigging` or excavating machine, and particularly'to animfprovedmechanism for driving the digging unit r"of a trenching orsimilar machine.

` This, therefore, is the general objectiof this invention.

A more specific object of this invention is the `provision of, a powertransmission* mechanism for a trench diggingmachine to drivinglyinterconnect the power plant with an adjustably positioned diggingmechanism, which transmission mechanismwill facilitate relative movementbetween the digging unit and the power plant without impairing theefficiency of the transmission 'of power, and which mechanism will beeconomical tomanufacture and easy to assemble.

A further object ofthis `invention is to provide an improved take-upmechanism for taking up the slack in a driving chain or belt, whichmechanism will be simple and economical to manufacture.

`Another object of the present invention is the Aprovision of atensioning device for `taking `up the slack a driving chain or belt andwhich will permitlthe` driving and :driven members to be moved relativeto ea-ch otherf-and wherein the tension on the chain or belt engagingmember ofthe device increases at an increasing rate for `each degree ofmovement of said member until the operating minimum tension is securedand thereafter such rate decreases for each degree of continued movementof the tensioning member.

Other objects and .advantages of this invention `will becomemore'apparent from the following "description, Vreference being hadtothe accompanying drawings which illustrate a preferred embodimentofthe invention. The essential and novel features of the invention willbe' summarized in the claims.

In the drawings, Figfl isia side elevation of a trench diggingmachinehaving my invention incorporated therein; Fig. 2 is'a sectional detail,

on an enlarged scale, theplaneof the section being indicated by thelines 2-2 on Fig. 1; Fig. 3

fois a` sectional view as indicated by the lines 3-3 f on Fig. 2, andFig. 4 is a diagram illustrating one of the features of my invention.

Referring again to the drawings, it will be seen that I have illustratedmy invention incorporated ina` trench digging machine of the rotarywheel type, The machine, as illustrated in Fig. 1, comprises a main`frame I mounted on a pair of tractor belts, one of which isshown at II. These belts lare driven by a motor I2 which is supported at theforward endof the frame, through 'the medium of a power transmissionmechanism 1 including a drive chain I4 and a tractor belt drive sprocketwheel I4a. At the rear end ofthe frame there is provided a verticallyextending guideway I5, and slidably mounted in this guideway isacarriage I6. Pivoted as at I'I to the carriage is an outwardlyextending boom or digging wheel frame I8.

The boom or digging wheel frame is raised and lowered and/or swung aboutits pivot I'I by cables 2l) and 2|. The cable 20 extends from a windingdrum 22 over one of a plurality of independent sheaves 23, mounted atthe upper end of the guideway; thence, rearward around a sheave` 24carried adjacent the outer end of the boom;` thence forward and aroundanother `one of the sheaves 23, and thence to the rearward end of theboom `where it is secured as at 25. The cable 2| extends fromfa windingdrum 26 up and over one of the sheaves 23; thence downward and `aroundasheave 21 carried by the pivoted end of ered, or swung about its pivotas indicated by the dotted'line positions I8a .and Ib of the boom.

The digging boom I8 supports a diggingunit. This unit comprises a pairof spaced rings which lare secured together by a series of U shapeddigging buckets 36. The digging unit or wheel is supported -by aplurality of rollers, two

`of which are shown at 31.

The digging wheel is driven by the motor I2.

` A powertransmission 38 connects the power l shaft 30 with a shaft 39carrying a sprocket wheel-4D. A drive chain 4I is connected between thesprocket wheel 40 and another sprocket `wheel 42 carried by a shaft 43on the boom. Also secured to the shaft 43 is a sprocketgear 44 `whichengages teeth formations 45 lcarried by the rings 35 of the diggingWheel. A conveyor belt, generally indicated at 46, extends through thewheeland may also be driven from the shaft 43 in any well known manner.

Inspection of the full and dotted line positions `.4ta and -4Ib of thedriving -chainfwhich propels `the digging wheel, will indicate therelative'positions of the sprocket wheels as well as the surplus ofdrive chain required. The present invention is particularly concernedwith the mechanism for taking up this surplus and eliminating slack inthe chain without permitting the upper and lower stretches of the chainto engage each other.

The take-up mechanism of the present invention is particularlyapplicable to the trenching machine heretofore described, as especialattention has been given to the particular relation of the movement ofthe driven sprocket 42 of the digging unit and the angular movement ofthe chain about the axis of the driving sprocket wheel 40 which togetherwith the take-up mechanism, about to be described, assist in themaintenance of substantially the same tension on the chain for allpositions of the digging unit.

The take-up mechanism is shown in detail in Figs. 2 and 3, while therelation of this mechanism to the trencher mechanism is shown in Fig. l.This mechanism is mounted on the supplemental frame or boom I8intermediate the digging wheel and the guideway I5. As illustrated inthe drawings, a tube 50 is provided at one end with a base plate I whichis secured to the -1 boom I8. A brace 52 extends between the upperregion of the tube and the boom, and assists in maintaining the tube ina vertical position. At its upper end the tube 50 is provided with anenlarged hollow housing 53 which carries a chain .engaging member andwhich is covered by a removable cover plate 59.

The 4chain engaging member comprises a pair yof arms 54 and 55 spaced bysleeves 55 positioned at opposite ends of the arms. Suitable bolts 51pass through the sleeves and arms to maintain secure assembly together.Rotatably mounted on each sleeve 56 is a chain engaging sprocket wheel58. The arrangement is such that the chain may pass beneath one sprocketwheel 58, thence between the arms and over the other sprocket Wheel.

The chain engaging member is mounted on the housing 53 at the top of thetube 50. Centrally secured to the arm 54 and extending outward therefromis a spindle or shaft 60 which is journalled in the housing 53. A pin 6Ipassing through the ,shaft 60 retains it in position in the housing.

Tensioning of the chain engaging member is accomplished by a coiledtension spring B5. The lo-wer end of the spring 65 is mounted on a` pin66 which extends through the lower portion of the tube. The springextends'upward in the tube and has its upper end secured to one end of aexible member such as a chain 6l, the other end of which is secured asat 68 to an eccentric 69. This eccentric comprises a shaft section whichis drivingly and eccentrically secured to the shaft 60.

It will be noted from the diagram of Fig. 4, that as the chain engagingmember is first rotated in a clockwise direction to tension the spring,the eccentric increases in length thus causing the spring to bestretched at an increasing rate of speed for each successive unit ofmovement of the chain engaging member about its axis. The relation ofthe length of the chain and spring, and the position of the eccentric issuch that the desired minimum tension in operation is secured when thelever arm of the eccentric is the longest or shortly thereafter.

Continued rotation of the chain engaging member 54, after the desiredminimum tension is acquired, causes the lever arm of the eccentric todecrease with each unit of rotation of the chain engaging member. Thiscauses the spring to be stretched at a decreasing rate of speed as thechain engaging member moves, and thus limits the increase of thepressure of the spring and, hence, the increase in tension on the chain.

The increasing and decreasing action of the lever arm of the eccentric69 is diagrammatically illustrated in Fig. 4. In this diagram theeccentric is shown in a plurality of successive positions, each positionbeing the same predetermined unit of angular rotation from the precedingposition. The horizontal lines 'l0 and II indicate the longest andshortest lever arms, respectively, of the eccentric. The lower ends ofthe vertical lines 'I2 indicate the relative position of the end of thechain or flexible member 61. Thus, it will be seen that if the chainengaging arm is swung at a constant rate of speed, the spring will bestretched at an increasing rate of speed until the high point of theeccentric is in a plane at right angles to the extent of the spring, andthen at a decreasing rate of speed until the extreme position of thechain engaging member is reached.

I claim:

1. A tensioning device for a exible driving member such as a chain orbelt, said device comprising a rotatable member having means to engagethe flexible member, an eccentric secured to said member, a tensionspring, flexible means connecting one end of said spring to saideccentric and adapted and arranged to be Wrapped around the periphery ofsaid eccentric consequent upon rotation of said rotatable member, andmeans aixing the other end of said spring at a fixed point remote fromsaid shaft.

2. A tensioning device for a flexible. driving member such as a chain orbelt, said device comprising a rotatable member having means to engageopposite sides of one reach of the flexible member at spaced points, ashaft carried by said member intermediate its ends, a support for saidshaft, an eccentric secured to said shaft, and a resilient stretchablemember, flexible means connecting one end of said resilient member tosaid eccentric and adapted and arranged to be wrapped around theperiphery of said eccentric consequent upon rotation of said rotatablemember, and means aixing the other end of said spring at a fixed pointremote from said shaft.

3. A tensioning device for a flexible driving mem-ber such as a chain orbelt, said device comprising a rotatable elongated arm having means atits opposite ends to engage opposite sides of one reach of the flexiblemember at spaced points, a shaft secured to said member, a support forsaid shaft, an eccentric drum secured to said shaft, a tension spring,means connecting one end of said spring to said eccentric drum at apoint remote from the axis of said shaft, and adapted and arranged to bewrapped around the periphery of said drum consequent upon rotation .ofsaid arm, and means aflixing the other end of said spring at a xed pointremote from said shaft.

4. A device of the character described, a frame, a coil spring, means atone end of said frame to fixedly position one end of said spring, ashaft rotatably mounted in the upper end of said frame and having itsaxis extending transversely thereof, an eccentric secured to said shaft,a flexible member having one end thereof secured to the upper end of:said spring and the other end secured to said eccentric, a pair ofspaced elongated arms secured intermediate their ends to said shaft andextending in a plane normal to an axial `plane passing through the axisof said shaft and the high point of said eccentric, and means carried byand between said arms and at opposite ends thereof to engage a chain orsimilar memend of said spring, a drum eccentrically mounted r in theupper end of said standard and having its axis extending transverselythereof, the upper end of said spring beingsecured to said drum, anelongated arm secured intermediate its ends to said drum and concentricwith its axis of revolution, and means on opposite ends of said arm toengage a chain or similar member.

6. A device of thecharacter described, a frame comprising a tubularstandard, a coil spring extending axially Within said standard, means atone end of said standard to fixedly position one end of said spring, ashaft rotatably mounted in the upper end of said standard andyhaving itsaxis extending transversely thereof, an eccentric drum secured to saidshaft Within said standard, a flexible member having one end thereofother end secured to said drum, said flexible member being arranged andadapted to be Wrapped about the periphery of said drum con sequent uponrotation of said shaft, an elongated arm securedintermediate its ends tosaid shaft exteriorly of said standard, andmeans on opposite ends ofsaid arm to engage a chain or similar member.

7. A device of the character described, a frame comprisingatubularstandard, a coil spring extending axially vWithin-said standard,means at one end of said standard to xedly position one` end of saidspring, a shaftI rotatably mounted in the upper end of said standard andhaving its axis extending transversely thereof, an eccentric drumsecured to said shaft within said standard, a exible member having oneend thereof secured to the upper end of said spring and the other endsecured to said drum, said flexible member being arranged and adapted tobe wrapped about the periphery of saidv drum consequent upon rotation ofsaid shaft, an elongated arm secured intermediate its ends to said shaftexteriorly of `said standard and extending in a plane normal to an axialplane passing through the axis of said shaft and the high point of saideccentric, and a sprocket Wheel rotatably mounted on each end of saidarm to engage a chain to be tensioned;

